In many localities, no sale and reliable water supply is available. A water distribution system may be lacking, or, frequently, such a system may exist but deliver water that is not or may not be safe and fit for drinking because it is contaminated, particularly by microorganisms. The problem of providing safe, potable water in such localities, has received wide attention and found a variety of solutions in the art.
Filtration is one of the means that can be used. In most cases, the filters used in water purification apparatus operate at constant pressure mode. viz. a filter is placed on a source of constant pressure and allowed to filter water until its rate of filtration is below some predetermined unacceptable value. In some cases, some degree of flow rate control is provided. For instance, U.S. Pat. No 5,503,735 discloses a liquid purification system which provides a reverse osmosis filter membrane in a filter cartridge. Not all of the water passes through the membrane and the water not passing through the membrane passes through a pressure relief valve which can be adjusted to vary the water pressure and flow rates in the system. Devices which maintain a constant flow rate and variable pressures are employed in the systems in which water flows, for instance, in irrigation systems. Processes for controlling the flow-through speed of the filter infiltration devices are also known. One such device is described in U.S. Pat. No. 5,238,559.
JP 06185070 (Kokai No. 5-185070) notes that in domestic water purifiers the filter module must be replaced when the water that has flown through it has exceeded the allowable absorption capacity of the absorbent inside the module, and that water purifiers are known which are provided with a life meter capable of displaying the time of replacing the filter module. However, the known devices are said to be unreliable because they measure only the time of the water flow and this does not provide a reliable indication due to fluctuations in the water flow rate. Therefore said application proposes a domestic water purifier which comprises a constant flow rate valve, a sensor for detecting start and stop of water flow and generating corresponding signals, and means for measuring an integrated operating time based on said signals and displaying a signal when said integrated time reaches a preset value. The application shows various structures of constant flow rate valves, but as to the filter module it shows no structure and states that the invention may utilize various structures of the prior art.
The filters used in water purification systems of the prior art, particularly those intended not merely to remove solid substances, but to remove microorganisms and render the water fully potable, are not fully satisfactory from several viewpoints. The throughput of the filters is usually low, so the filters must be changed frequently. The filters must have a large surface area. Since microporous membranes are required for the removal of microorganisms, such filters are very expensive.
It is a purpose of this invention to provide a filter device that is adapted for purifying water, and which is free of the defects of the existing devices.
It is another purpose of this invention to provide a filter element for making such a filter device.
It is a further purpose of this invention to provide a process for making such a filter element and filter device.
It is a still further purpose of this invention to provide a method for optimizing the operation of said filter device.
Other purposes and advantages of the invention will appear as the description proceeds.